In a state where a presidential election was famously decided by 537 ballots, Florida Democrats’ edge of 485,907 active voters over registered Republicans looks impressive at a glance.

But it isn’t.

In historical terms, it’s a bad sign for Democrats and Charlie Crist. And it’s great news for Republicans and Gov. Rick Scott.

The Democrats’ registration advantage hasn’t been this small since 2007. Perhaps more significantly, the gap is even smaller than it was in 2010 (591,809), when Republicans whipped Democrats at the ballot box.

You wouldn’t know the Democrats’ precarious position by looking at the public-opinion polls right now or by listening to Crist.

“I think we're gonna do it,” Crist told state House Democrats in Tallahassee on Thursday. “And I think they know it."

By “they,” Crist means Republicans. He used to be one of them (before becoming an independent and then a Democrat).

“They” don’t think they’re going to lose at all. There’s a reason for the Republican confidence: history.

Yes, the Republican base is proportionately shrinking. It’s growing whiter, while Florida gets browner. And it’s a problem for the GOP in presidential election years when young people and minorities cast ballots in bigger numbers.

But there’s one advantage to having a large bloc of white voters during a mid-term election: They vote far more often and in bigger proportions than minorities.

Also, because the GOP controls the state power structure (determined in mid-term election years) it’s able to raise far more money than Democrats. That’s why in the last fundraising quarter, announced late last week, Scott’s side was able to raise $17.1 million to Crist’s and the Democrats’ $6.1 million.

For Democrats, that’s just not enough money to both run a statewide race and conduct the type of voter registration efforts that President Barack Obama did twice in Florida to help guarantee a win.

Had it not been for the nearly 300,000 new voters Obama’s campaign helped register in 2012, he likely would have lost Florida. Then, Democrats outnumbered the GOP by 535,987 active registered voters. The Democrats’ registration advantage peaked after the 2008 election (657,775) and has been declining ever since.

Since the 2012 race, the Democrats’ registration lead has been cut by about 9 percent, in large part due to attrition. Dead people, former felons and some voters classified as “inactive” who appear to have moved and don’t then cast ballots in two general elections, for instance, are removed from the rolls. So it’s not that Republican ranks are growing; they’re just shrinking more slowly than the Democrats’ rolls.

Meantime, new voters are increasingly registering as no-party-affiliation/independent voters.

Even in presidential election years, Republican performance (the percent who actually show up and vote) is proportionately superior to that of registered Democrats.

But when Democrats show up in force, all the proportionality in the world can’t save the GOP. Even those elections aren’t blow-outs.

So if anyone wonders why many think this governor’s race could be a coin toss (perhaps rivaling the disputed 2000 presidential election decided by 537 votes), it’s because this is what history shows us: